Safety device for systems of distribution



(No Model.)

H. G. WIRT. SAFETY DEVICE FOR SYSTEMS 0P DISTRIBUTION.

No. 499,275. Patented June 13, 18.93.

WITNESSES: INVENTOR:

ATTYS.

NITED, STATES PATENT OFFICE.

HERBERT O. \VIRT, OF BOSTON, MASSACHUSETTS.

SAFETY DEVICE FOR SYSTEMS OF DISTRIBUTION.

SPECIFICATION forming part of Letters Patent No. 499,275, dated June 13, 1893.

Application filed March 16, 1892. Serial No. 425,109. (No model.)

To all whom it may concern:

Be it known that I, HERBERT G. WIRT, a citizen of the United States, residing at Boston, county of Suffolk, State of Massachusetts, have invented a certain new and useful Improvement in Systems of Distribution, of which the following is a specification.

My present invention has to do with electric distribution systems, and especially those employing currents of high tension, as for example, are light circuits or alternating current transformer systems. When a shock is received from a circuit of this character it is likely to be fatal, and my principal object is to so modify the system that this danger now attendant on the use of high voltages may be obviated. I do not remove the liability to receiving a shock but, by grounding the generator as hereinafter described, the voltage of the shock it is possible to get is brought within such limits that loss of life need not be feared.

The invention provides a fault indicator to indicate at the central station the existence of a ground upon the line, and the arrangement furthermore is such as to automatically cut out a section upon its becoming grounded. The mode of attaining these results will be clearupon an examination of the devices illus trated in the accompanying drawings,wl1ere- 1n Figure 1 is a diagrammatic view of the in vention, and Fig. 2 is a similar diagrammatic View, diifering from Fig. 1 mainly in illustrating the invention applied to a multiple rather than a series circuit.

Arepresents a generatorof electricity,which is here represented as an alternating current generator having a number of armature or generating coils B connected in series as is customary in such machine. The terminals of the series of coils are brought to collecting rings 0 and D on which bear brushes a and 1) leading to the external circuit E. This circuit is normally insulated from ground, and contains arc lamps or other desired translating devices F arranged either in series as shown in Fig. 1, or in multiple as in Fig. 2. At a point G approximately midway electrically between the terminals of the machines a connection is made from the coils to a third collecting ring H, which is insulated from the a shock of great severity.

other rings and dynamo shaft and is permanently grounded through a brush 7L. Hence there will be a difference of potential between the ring H and rings C andD of only about one half that existing between the terminals of the machine at the rings C and D, and a shock re ceived through a short-circuit including the ring II will be correspondingly less severe than were the entire machine short-circuited. In this fact is to be found an essential difference between the present invention and the prior art.

In prior systems there has constantly existed the danger of a shock of the entire, or practically the entire, voltage of theline. In the system now proposed the same high line voltage may be retained with all the attendant advantages making such practice desirable, and yet the voltage which will be received by any one accidentally grounding the line may be reduced one half. A thousand volt circuit, for example, may thus be rendered practically as safe as a five hundred volt circuit heretofore, and the chief objection to high tension systems be thus largely removed. To make this clear, suppose an ordinary circuit with my permanent ground connection absent, then should an accidental ground occur at some portion of the line J, no indication will be given and its existence will not beknown, but the condition of affairs remain such that any one establishing a second ground connection as at J must receive Now if the generator be permanently grounded in the manner described, a shock may indeed be received upon an accidental grounding of the line, but the shock will be much less severe because as has been explained the difference of potential between the ring H and the terminal rings 0, D is only a fraction of that which exists between the rings 0 and D.

To indicate at the central station the existence of a ground upon the line, magnet I is provided in the ground branch. \Nhen such ground occurs the flow of current through the short-circuit thus established energizes momentarily the magnet even on an alternating current circuit. The armature dis attracted, tripping the vane or indicator 1;, and permitting it to fall into a vertical position, where it remains until reset. In Fig. 1 a fuse or like circuit interrupter g is also placed in the ground connection which breaks the shortcircuit automatically after the desired indication of its existence has been given, so that the lights at most are only momentarily extinguished.

Referring now to Fig. 2, the translating devices are shown arranged in multiple arc branches L, and each subcircuit is connected to the mains M, N by fuses or circuit interrupters such as placed in the ground connection in Fig. 1. Vith a multiple circuit they are preferably arranged at this point in order that the entire sub-circuit grounded may be cut out until the fault is found and repaired. As will be understood from the foregoing explanation, if a shock is experienced by shortcircuiting the mains M, N, or the opposite wires of one of the sub-circuits, the full volt age of the machine will be felt, but by permanently grounding the generating coils the danger of fatal consequences is greatly lessened, and in fact, in such circuits as are now installed, is practically done away with altogether.

What I claim as new, and desire to secure by Letters Patent, is

1. The combination of an electric circuit normally insulated from ground, with a source of electricity of high tension connected therewith, and permanently grounded at an intermediate point where the Voltage is only a fraction of the total voltage between the circuit terminals, as set forth.

2. The combination of an electric circuit normally insulated from ground, with a generator of electricity having one or more generating coils or sets of coils connected in series, and a connection normally grounding such coils at a point approximately midway electrically between the circuit terminals, as described.

3. An alternating current generator having its generating coils arranged in any ordinary manner, and connected at an intermediate point between the circuit terminals to a collecting ring or brush by which such coils are grounded, as described.

4. The combination of an electric generator normally grounded at an intermediate point between the circuit terminals so as to form a short-circuit upon the occurrence of a ground upon the line as described, with a safety catch or like automatic circuit interrupter arranged to form part of such short-circuit when established, and to automatically rupture it as set forth.

5. The combination of an electric generator normally grounded at an intermediate point between the circuit terminals and adapted to establish a short-circuit upon the occurrence of a ground on the line as described, with an indicator at the central station responding to, and indicating the existence of such a shortcircuit, as set forth.

In testimony whereof I have hereto set my hand this lath day of March, 1892.

HERBERT O. \VIRT.

lVitnesses:

C. L. HAYNES, A. M. OUSE. 

